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Management Alternatives for Reverse Osmosis Leachate Treatment Concentrate David Pannucci(1) and Arie Kremen(2) (1) Progressive Waste Solutions

(2) Cornerstone Environmental

May 17, 2016

FNYSWA Spring Conference The Sagamore, Bolton Landing, New York

Leachate Disposal Cost (Cap & Op Ex)

© 2016 Cornerstone. All rights reserved.

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Old and closed Landfills

Operating Landfills

MSW Leachate Characteristic Composition


Young Medium Old Age (yr) <1 1-5 >5 pH <6.5 6.5-7.5 >7.5 COD (mg/l) >15,000 3,000-15,000 <3,000 BOD5/COD 0.5-1.0 0.1-0.5 <0.1 TOC/COD <0.3 0.3-0.5 >0.5 NH3-N (mg/l) <400 400 >400 Metals (mg/l) >2.0 <2.0 <2.0 Organic Compounds 80% VFA 5-30% VFA, HA,

FA HA, FA

(VFA – Volatile Fatty Acid, HA – Humic Acid, FA – Fulvic Acid)

Specific Leachate Production: 180 – 200 gallon/acre/day

Evolution of Organic Constituents


Landfill Gas

Leachate

McBean and Rovers (1998) Statistical Procedures for Analysis of Environmental Monitoring Data and Risk Assessment, Prentice-Hall Publishing Co.

young Landfill Age medium old

• BOD • COD Biodegradable

• BOD/COD Recalcitrant

• Ammonia Nitrogen, Phosphorus

• Benzene, Vinyl chloride, … • Arsenic, Lead, ….

Organic Pollutants, Heavy Metals

• Total Dissolved Solids (TDS) • Electrical Conductance

Chloride, Sodium, Potassium, Calcium

Contaminant Classification


Biochemical Organics

Nutrients

Salts

Trace Pollutants

Solid Separation: Size Comparison


Particulate Colloid Dissolved

Reverse Osmosis

Osmosis: movement of water through a semi-permeable membrane to equalize solute concentration

Reverse Osmosis: application of external pressure, forces water to the low concentration side

© 2015 Cornerstone. All rights reserved. 7

Reverse Osmosis vs. Filtration: filtration relies of size exclusion, whereas RO is also relying diffusion and pressures

Dissolved Organics in Leachate Effluent


Effluent 1.5μm .45μm .22μm 100kDa 30kDa 10kDa 5kDa 3kDa 1kDa 500Da

Source: John T Novak, PhD Virginia Polytechnic Institute

Reverse Osmosis Filtration

RO Design Rules of Thumb

• Recovery is a design parameter

• Higher recoveries: Lower concentrate volume

Lower quality permeate

Accelerated membrane fouling and scaling

• Fouling, buildup of particles and colloids on membrane


Recovery Concentration Factor

50% 2 75% 4 80% 5 83% 6


Membrane Performance

20ppm 40ppm 80ppm

Permeate Concentration Recovery

Feed/Concentrate Concentration

80% Rejection

Membrane

0%

50%

75%

100 ppm

200 ppm

400 ppm

Species Rejection* Ammonium 80-90% (pH<7.8) Chloride 92-98% Sodium 92-98% Potassium 92-96% Calcium 93-99% Iron 96-98% Sulfate 96-99% Borate 30-50% Cyanide 90-99% Magnesium 93-98% Phosphate 96-98% * Polyamide composite membrane at 25°C

Real World Example


Parameter (mg/l) Leachate Concentrate Concentration Factor

NH3-N 1,831 4,951 2.70 NO3, NO2-N 0.251 0.797 3.18 BOD 3,509 7,405 2.11 COD 7,934 20,032 2.52 TDS 15,150 38,606 2.55 Sulfate 120 12,812 107 Conductivity (μS/cm) 40,971 60,956 1.47

Concentration Factor (avg.) 2.6 Recovery (calculated) 62% 𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 = 𝑃𝑅𝑅𝑃𝑅𝑃𝑃𝑅 𝐹𝐹𝑅𝐹 𝐹𝑅𝑅𝐹𝐹𝑃𝑅𝑅𝐹 𝐹𝐹𝑅𝐹⁄

Seawater:

>35,000

>50,000

Concentrate Management Options

• Offsite disposal

• Onsite treatment • Multistage RO

• Evaporation

• Solidification/Resource Recovery

• Eutectic Freeze Crystallization


Offsite Disposal

• Compared to sanitary wastewater, RO concentrate is … concentrated:


Parameter (mg/) RO Concentrate

typ. Sanitary Wastewater

Enrichment Factor

NH3-N 4,951 20 x250 BOD 7,405 250 x30 TDS 38,606 500 x75 Conductivity (μS/cm) 60,965 500 x120

• Requires large design-flow POTW to rely on dilution

• Subject to monitoring and discharge limitations, e.g.: • Metals, Volatiles, recalcitrant COD, Dissolved Organic Nitrogen

• Cost

Cascading RO Stages

Objective: Reduce concentrate volume

Constraint: Maintain membrane cross-flow velocities

Diminishing returns, increasing costs


0

50

100

150

200

250

300

0

0.5

1

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0 1 2 3 4 5 6 7

Con

cent

rate

(ppm

)

Per

mea

te (p

pm)

RO Stage

Recovery Rate of 62% is result of dual stage RO with optional permeate polishing:

Greater concentrate reduction not economically feasible.

Real World Example (cont’d)


Electrodialisys Reversal (EDR)

Electric current migrates ions through an electrodialysis stack of altering cationic and anionic ion exchange membranes.

• Feedstock recovery rate: 90+% (water supply);

• Self-cleaning through periodic voltage reversal;

• Applications: water supply, brine concentrator


• Nitrate • Total Dissolved Solids • Arsenic • Sulfate • Iron • Radionuclides • Sulfate Con

tam

inan

ts

EDR-RO

• Generates highly concentrated brine;

• Relative to RO: higher CapEx, lower OpEx

• Less susceptible to fouling and scaling;

• Dual purpose Hybrid EDR-RO: • Feedstock pre-treatment (softening)

• Concentrate post-treatment (brine concentration)

• No commercial installation (Leachate Concentrate);


Concentrate

EDR RO

Vapor Compression Distillation (VCD)

• VCD recovery exceeds 90%, in combination with crystallizer can achieve ZLD;

• Processes feedstock with TDS up to 650 g/l;

• Operating concept: 1. Compression increases vapor pressure 2. Increases condensation temperature 3. Vapor temperature is used to preheat feedstock; 4. Feedstock is vapor source;

• Opportunity cost: $0.02/gal (LFG)

• Op Ex: $0.02-$0.04/gal (VCD only)


Salt Crystallizers

• Commodity salt crystallizers operate on neat brines;

• Leachate RO concentrate contains large number of dissolved minerals;

• Relatively few Mixed Salt Crystallizers (15 units) operate in North America (2011, GE);

• Crystallizers are added to VCD units to achieve ZLD;

• Crystallizers are constructed from high grade metals or plastics;

• Crystallization is very energy intensive;


Misting enhanced Evaporation


Residue from Leachate Evaporator (‘Misting’)

Thermally Enhanced Evaporation

• Leachate volume by up to 95%: • Evaporation vessels;

• Direct injection-devices;

• Metals precipitate, fall out as salts;

• Organics are volatilized and stripped by vapor;

• Energy intensive, requires LFG or waste heat;

• Residuals: slurry (vessel) or grit (direct injection);

• Esthetic impact: steam plume;


• Approx. 24 scf LFG/gal

• Residual volume: 3-10% of feedstock

• Residual solid content: 10-12% (slurry)

• Disposal at working face

• Air Quality permitting

• Op Ex: $0.055-$0.065/gal

• LFG Opportunity cost

Evaporation Vessel


Ammonia Recovery & Uses

• Stripping: ammonium sulfate formation • Requires pH adjustment, absorption by sulfuric acid

• Uses: fertilizer, agricultural spray adjuvant

• Solidification: struvite precipitation (‘kidney stones’) • Requires: magnesium, phosphate, pH adjustment

• Uses: fertilizer

• landfilling


Struvite

Thermodynamic Considerations


Parameter Value Specific Heat of Water 4.2 kJ/kg/K Enthalpy of Evaporation 2,257 kJ/kg Enthalpy of Fusion 334 J/kg

50°C/106°F 8,920 Btu/gal 18 scfm LFG/gal

2,025 Btu/gal 4 scfm LFG/gal

x7

Eutectic System


Salt Concentration (%wt) CEutectic

T Eut

ectic

Te

mpe

ratu

re

Solution

Ice & Salt

Salt & Solution Ice & Solution

Eutectic Point

A B

Thermodynamic equilibrium point where a salt and its solution transition from solid to liquid state

Summary

• RO can achieve direct discharge limitations

• Challenges: concentrate volume, TDS, and ammonia

• Multiple ionic species increase complexity

• With exception of evaporators, industry has limited experience treating Leachate RO Concentrate

• Consider Total Cost of Ownership, incl. opportunity cost

• Rights and ready access to waste heat can affect project economics


Questions? Comments?


Arie Kremen, PhD [email protected] 845.695.0213

David Pannucci, PE [email protected] 315.539.5624

mailto:[email protected]

mailto:[email protected]

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